1. What is the isoelectric point of tyrosine? Draw out the different structures of tyrosine at each pka.2. Draw the tripeptide containing Ser-Ala-Val.

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Human Heredity: Principles and Issues (MindTap Course List)

11th Edition

ISBN:9781305251052

Author:Michael Cummings

Publisher:Michael Cummings

Chapter9: Gene Expression And Gene Regulation

Section: Chapter Questions

Problem 15QP

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1. Consider the following α helix from myoglobin at pH 7. Gln-Gly-Ala-Met-Asn-Lys-Ala-Leu-Glu-His-Phe-Arg-Lys-Asp-Ile-Ala-Ala-Lys-Tyr(a) Label amino acids in the polypeptide above as follows: p for polar and uncharged, np for non polar, – for negatively charged, and + for positively charged.(b) How many complete turns are there in this helix?(b) Which side chains are likely to be on the side of the helix that faces the aqueous solvent? Why?(c) Which side chains are likely to face the interior of the protein? Why?
6) Proteins can be modified by phosphorylation, which adds a phosphate group to the hydroxyl group of serine, threonine, or tyrosine residues. The R-group for phosphoserine is shown at right. A) The image below is an Isoelectric focusing strip that shows the unphosphorylated protein-of-interest (in blue). To which side of the unphosphorylated protein would you expect to see the phosphorylated protein? (Draw an arrow to indicate direction). Briefly justify your answer. un-phosphorylatable: Low pH Justify: B) To study the effects of phosphorylation, researchers often mutate a Ser/Thr to appear as though it is always phosphorylated or never phosphorylated at a particular site. What amino acid substitution should you use to preserve similar dimensions as Ser (or Thr) but make the side chain appear to be: constitutively (always) phosphorylated: Justify: Ser or Thr → O O=P-O O I CH₂ Ser or Thr➜ Phosphoserine High pH
2. Consider the peptide Trp-Arg-Glu-Cys-Gly-Tyr. For the drawings requested below, please show in zig-zag style, from amino to carboxy terminus, with correct stereochemistry a. Draw the predominant form at pH = 2 b. Draw the predominant form at pH = 5 c. Draw the predominant form at pH = 7 d. Draw the predominant form at pH = 12
1. In the separation of lysine from histidine using a sulfonated polystyrene column will it be easier to separate at pH 4 or pH 8 ? explain! 2. A peptide of the order Glx-Ala-Gly-Arg bound to a sulfonated polystyrene column at neutral pH. Is Glx Glu or Gln ? Explain !
1. Amino acid analysis of the peptide gave the following residues: Asp Leu Lys Met Phe Tyr. The following facts were observed: Trypsin treatment had no effect. The phenylthiohydantoin released by Edman degradation was C-C-CH2. Brief chymotrypsin treatment yielded several products including a dipeptide and a tetrapeptide. The tetrapeptide contained Leu, Lys and Met is some order. Cyanogen bromide treatment afforded a dipeptide, a tetrapeptide and a free Lys. What is the amino acid sequence for this heptapeptide?
For the peptide Ala-Cys-His-Ile-Leu-Asp a. Write the single letter code for the amino acid residues b. What is the charge of the peptide at pH 7.0. Assign the following pKa values: 3,4,6,8,9 c. What is the pI of the peptide
1. A pentapeptide has the sequence of H2N-Glu-His-Leu-Arg-Gly-COOH. a) What is the net charge of the peptide at pH 3, 8, and 11? (Use pka values for side chains and terminal amino and carboxyl groups in the table provided.) peptide. b) Estimate the pl for this pK, values Abbreviation/ symbol pk, M, (-COOH) (-NH5) (R group) pK; pKR Hydropathy Occurrence in index* proteins (%)* Amino acid pl Nonpolar, aliphatic R groups Glycine Alanine Proline Valine 2.34 -0.4 Gly G Ala A Pro P 75 9.60 5.97 7.2 89 115 2.34 9.69 10.96 6.01 6.48 5.97 1.8 1.6 4.2 3.8 4.5 7.8 5.2 1.99 117 131 Val V 2.32 2.36 9.62 9.60 6.6 9.1 Leucine Leu L 5.98 Isoleucine lle I 131 2.36 2.28 9.68 6.02 5.3 Methionine Met M 149 9.21 5.74 1.9 2.3 Aromatic R groups Phenylalanine Tyrosine Tryptophan 2.8 -1.3 3.9 3.2 Phe F 165 1.83 9.13 9.11 9.39 5.48 2.20 Tyr Y Trp W 181 10.07 5.66 204 2.38 5.89 -0.9 1.4 Polar, uncharged R groups Serine Ser S 105 2.21 6.8 9.15 9.62 5.68 5.87 5.07 5.41 5.65 -0.8 Threonine Thr T 119 2.11 -0.7 5.9…
C00- *H3N -C-H CH2 он Tyrosine a. Draw the structures of tyrosine as different pH values. Please refer to the lecture notes for the pKa values b. Identify the structures that exist at pH 2 c. Solve for the pl
Porcine dynorphin is a neuropeptide having 17 amino acid residues. Its structure is shown below. Tyr-Gly-Gly-Phe-Leu-Arg-Arg-Ile-Arg-Pro-Lys-Leu-Lys-Trp-Asp-Asn-Gln 8. How does trypsin catalyze the hydrolysis of peptides? You can answer this question by identifying the amino acids involved and whether the hydrolysis is at their amino side or the carboxyl side or if particular amino acids end up at the N-teminal end or at the C-terminal end. 9. List down the different fragments that would result if dynorphin were cleaved by trypsin. 10. How does chymotrypsin catalyze the hydrolysis of peptides? You can answer this question by identifying the amino acids involved and whether the hydrolysis is at their amino side or the carboxyl side or if particular amino acids end up at the N-teminal end or at the C- terminal end. 11. List down the different fragments that would result if dynorphin were cleaved by chymotrypsin. 12. Cyanogen bromide is a chemical reagent which also cleaves peptide bonds.…
Make use of the table below in answering the questions asked: Amino acid pK₁ pK₂ pK, Isoleucine 2.32 9.76 Leucine 2.32 9.74 Lysine 2.16 9.06 10.54 Tyrosine 2.20 9.21 10.46 I 1. Make sure to answer in two decimal places. What is the pl of the tripeptide ILY? 2. At pH 9.00, at which electrode will the ILY tripeptide be moving to? A. Anode B. Cathode C. The tripeptide will not move to either electrodes Make sure to show a solution or explanation for the answer.
Amino acids project from each polypeptide backbone in a β-sheet in an alternating fashion (oneabove the plane and the next below the plane – see Fig 3.8B). Consider the following proteinsequence: Leu-Lys-Val-Asp-Ile-Ser-Leu-Arg-Leu-Lys-Ile-Arg-Phe-Glu.a. Is there a pattern to these amino acids? If so, what is it? b. What does this sequence of amino acids mean for the hydrophobicity/hydrophilicity of theresulting β-sheet? c. Can you make a prediction about how the β-sheet will be arranged in higher levels of protein structure? If so, what prediction would you make?
1. What is the length in AA’s of the LilP protein? Assume fMet is NOT CLEAVED. 2. Write out the sequence of the polypeptide in AA: use the three letter notation, e.g. Met-Ser-Pro-

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